Power Steering Gear Angle Detection via Dual Magnetic Sensing
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Solution Overview
Problem
Conventional power steering apparatuses face issues with inaccurate steering angle sensing due to careless assembly of gears, leading to deviations between the absolute steering angle output and the actual steering angle, especially when calibration values fail.
Innovation Solution
A power steering apparatus with a sensor housing containing a first gear and a second gear, each with magnetic members and mark portions, where the gears are designed to maintain a predetermined position relationship, and a microprocessor calculates the absolute steering angle using the rotation angles of these gears, ensuring accurate steering angle detection even without correct calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If gears are assembled without consideration of rotation angles, then assembly complexity is reduced, but steering angle accuracy deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-setting the rotational positions of the first and second gears relative to each other during assembly. The first gear is rotated by a predetermined angle relative to the second gear before mounting the detection elements, so that the initial rotational angles are already optimized for accurate steering angle detection, eliminating the need for post-assembly calibration adjustments
Solution Approach 2:
The patent changes the rotational angle parameter of the gears relative to each other. By rotating the first gear by a specific predetermined angle relative to the second gear, the system optimizes the initial state of the angle sensors to minimize measurement errors, thereby improving steering angle accuracy without complicating the assembly process
2Measurement precision
If calibration values are used to correct steering angle sensor output, then steering angle accuracy is improved, but system reliability deteriorates when calibration data is lost
Solution Approach 1:
The patent applies self-service by designing the system to automatically compensate for gear assembly variations through its own structural configuration. The predetermined rotational angle relationship between gears, combined with the angle difference calculation method, enables the system to self-correct for assembly tolerances without relying on external calibration data stored in non-volatile memory, ensuring continuous operation even when calibration data is lost
3Measurement precision
If calibration process is implemented, then steering angle accuracy is improved, but device complexity increases
Solution Approach 1:
The patent extracts the calibration function from the system by eliminating the need for separate calibration procedures. Instead of using stored calibration values to correct errors, the system directly calculates the steering angle from the angle difference between the two gears, which is inherently accurate due to the predetermined rotational relationship. This removes the calibration subsystem and simplifies the overall device
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design minimizes the difference between the absolute steering angle and the actual steering angle, preventing unnatural steering feelings and ensuring safe operation even during calibration failures, while simplifying the device and reducing size.
Implementation Method 1
a first magnetic member in which an N pole and an S pole are magnetized around a rotation axis that is a center, and which is arranged to be rotated in accordance with a rotation of the steering wheel
Implementation Method 2
a second magnetic member in which an N pole and to an S pole are magnetized around a rotation axis that is a center, and which is arranged to be rotated in accordance with the rotation of the first gear
Data Source
AI summary
A power steering apparatus includes: a first detection element arranged to sense a rotation angle of the first gear based on a variation of a magnetic field generated by the first magnetic member; a second detection element arranged to sense a rotation angle of the second gear based on a variation of a magnetic field generated by the second magnetic member; an absolute steering angle calculating circuit configured to calculate an absolute steering angle of the steering wheel from an neutral position of the steering wheel at which the steered wheel directs in a straight direction, by a combination between the rotation angle of the first gear and the rotation angle of the second gear; and a control section configured to drive and control the electric motor based on the absolute steering angle.